Control valve mechanism



Oct. 6, 1953 R. J. HOPKINS I 2,654,333

CONTROL. VALVE MECHANISM Original Filed May 1. 1948 4 Sheets-Sheet 1 Oct.6,1953 R. J. HOPKINS 4,

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Oct. 6, 1953 R. J. HOPKINS CONTROL VALVE MECHANISM Original Filed May 1, 1948 4 Sheets-Sheet 4 as E1913.

x A w- 30 z Fatented at. 6, i153 ,ts asi CONTROL VALVE MECHANISM Richard J. Hopkins, Franklin, Pa., assignor to Joy Manufacturing Company, Pittsburgh, Pa., a corporation of Pennsylvania Application February 25, 1953, Serial No. 338,790,

which is a continuation of tion Serial No. 24,558, May 1, 1948.

abandoned applica- Divided and this application February 18, 1950, Serial This invention relates to improvements in con- Drive and control means for the reel must be provided so that the reel shall wind up the cable when the car is moving towards the point of connection of the cable to a source of power and shall permit the drawing offof the cable when the car is moving away from the point of connection, and also such that, when the car moves in courses or paths which involve a need for shifting from a winding in to a paying out operation, or vice versa, this will be automatically accomplished. It is, moreover, important that when paying out ceases, conditions shall immediately be established in readiness for a winding in operation, in order to prevent possibility of the cables being run over, and to prevent an accumulation of slack which might interfere with the smooth winding of the cable. Additionally, accordingly, it is important to maintain some tension on the cable even during the time when it is being pulled on of the reel.

A very desirable apparatus for accomplishing the objectives mentioned is described and claimed in my application Serial No. 338,790, filed February 25, 1953, which is a continuation of my nowforfeited application, Serial No. 24,558, filed May 1, 1948, for Cable Reeling Mechanism of which application this present one is a division. That apparatus, in its illustrative form, includes a pump for supplying a hydraulic fluid, a motorpump device to which the pump supplies fluid and which is operatively connected to the reel so that when such motor pump device operates as a motor it drives the reel and so that it is driven by the reel when cable is unwound, together with means-the improved valve means of this present divisional application, in the illustrative embodimentcontrolled entirely by hydraulic pressures produced in the normal operations of the device for imposing on the motor-pump device a substantial pressure, say, for illustration, but without limitation thereto, 300 p. s. i. when the reel is being driven in the winding in direction; a pressure on the order, but without limitation thereto, of 100 p. at during unwinding of the cable; and a pressure, again on the order, but without limitation thereto. of 300 p. s. i. when the 13 Claims. (CL 137-102) reel is stationary, the latter pressure being automatically imposed upon the motor-pump device immediately after the reel comes to rest after an unwinding operation. Such valve means 'also permits the free discharge, substantially without any back pressure, of the full volume of fluid displaced by the pump when the reel or drum is not being driven by the motor-pump device but is instead driving the latter as a pump and causing the fluid then pumped thereby to be discharged against a back pressure imposed upon the motorpump device when cable is being drawn oil of the reel.

In a preferred embodiment of the invention, appropriate casing means may be provided having a supply passage, a vent passage, and a passage for connection to a device to be controlled, a pair of pressure relief valves set at different pressures, a check valve, and a shifter valve, the pressure relief valve having the higher setting having its supply side constantly in free communication with the supply passage and its discharge side constantly in free communication with the vent,

said check valve also having its supply side constantly in free communication with the supply passage and its discharge side constantly in free communication with the passage for connection to a-device to be controlled, the pressure relief valve having the lower setting havingits discharge side constantly in free communication with the vent and having its supply side connectible under the control of said shifter valve with the passage for connection'to a device to be controlled, and said supply passage also connectible with the vent under the control of the shifter valve, said shifter valve subjected at its opposite ends respectively to the pressure in the supply passage and in the passage for connection to a device to be controlled, whereby said valve is moved oppositely in accordance with whether the pressure is the greater in the former or in the latter passage. and said shifter valve in one extreme position connecting the supply passage with the vent and concurrently connecting the passage for connection to a device to be controlled with the supply side of the check valve having the lower setting and, past the latter, with the vent, and in the other extreme position interrupting communication between the passage for connection to a device to be controlled and the pressure relief valve having the lower setting, the check valve then opening to connect the supply passage with the passage for connection to a device to be controlled, means being provided for yieldingly biasing the shifter valve towards the latter position, and means being provided for the interconnection, through a restricted passage, of the supply passage and the passage for connection with a device to be controlled when, but only when, there is a connection between the supply passage and the vent passage effected by the movement of the shifter valve by pressure in the passage connected with the device to be controlled, whereby efiective shifting of the shifter valve shall at all times be effected.

An object of the invention is to provide an improved valve mechanism. Another object of the invention is to provide an improved valve mechanism particularly adapted, but not limited, to the control of a hydraulic reel driving and control mechanism for vehicles supplied with power through a trailing cable. A further object of the invention is to provide an improved control valve apparatus including a plurality of pressure relief valves, a hydraulically controlled P shifter valve for rendering one or the other of said relief valves effective, and means for providing a sharp and definite movement of the shifter valve regardless of the viscosity of the hydraulic fluid employed. Other objects and advantages of the invention will hereinafter more fully appear.

Referring to the drawings in which a preferred embodiment and two modifications of my invention are shown,

Fig. 1 is a diagrammatic view illustrating a form of fluid circuit and elements associated therewith for driving and controlling a motorpump device operatively connected with a cable reel, one of said elements being an illustrative a embodiment of my present invention.

Fig. 2 is an enlarged top or end view of the relief and control valve mechanism shown in Fig. 1, the view being taken from what might be called the top, if the parts shown in Fig. 1 be considered to have the same relationship in space as is indicated on the first sheet of the drawings.

Fig. 3 is a side view of the relief and control valve mechanism of Fig. 2, the view being from the left hand side thereof with the mechanism in the position indicated in Fig. 1.

Fig. 4 is another side view of the relief and control valve mechanism, the position corresponding to that of Fig. 1, but the scale being larger.

Fig. 5 is an enlarged sectional view 'on the plane of the section line 5-5 of Fig. 4, through the relief and control valve mechanism.

Fig. 6 is an enlarged sectional view taken on the plane of the line 6-6 of Fig. 3.

Fig. 7 is a sectional view on the same plane and scale as Fig. 5 but with the parts shown in different relative positions.

Fig. 8 is a sectional view on the same plane as Figs. 5 and 7, showing the shifter valve in still another position, the right hand portion of the valve mechanism being broken away.

Fig. 9 is a fragmentary sectional view taken on the plane of the line 9-9 of Fig. 5.

Figs. 10 and 11 are views similar'to Fig. 1 but showing the relief and bypass valve mechanism in a developed or schematic manner so that all of the passages therethrough and elements thereof may be noted in their working operations.

Fig. 12 is an enlarged sectional view on a plane corresponding to the plane of the section line 5-5 of Fig. 4, showing a modified relief and control valve mechanism.

Fig 13 is a sectional view on the same plane Fig. 15 is a sectional view on the same plane and scale as Fig. 14, with parts shown in different relative positions.

Referring now to the drawings, and first to Figs. 1, 10 and 11, it will be noted, as a preliminary to the detailed description of the control valve mechanism which is the subject matter of the present application, that a reservoir or tanl: l constituting a source of hydraulic fluid is provided to contain the necessary quantity of such fluid for the driving and controlling of a cable reel 9. It may, of course, constitute a source of fluid for other purposes, but with that I am not here concerned. The reservoir l is connected by a suction line 2 with a main pump 3, which is driven from any suitable source of power, not shown, and which is desirably driven whenever power is being delivered to the vehicle (not shown) on which the reel is supported. The pump 3 delivers fluid to a line 4 which is connected with a relief and shifter valve mechanism generally designated 5, which has a connection 6 leading to a motor-pump device I. This motorpump device I is operatively connected as by a belt or chain 8 with the cable reel 9, upon which a power supply cable I0 is wound. While my invention is specifically described with reference to a cable reel carrying an electric cable for supplying current to electric motors, the invention is not limited to such systems, but includes within its contemplation reels for flexible conductors for other operating media. The motor-pump device 1 is connected with a line or conduit H. which leads back to the reservoir or source I, and a relief line I3 leads from the valve mechanism 5 to the line II. The pump 3 is shown as the intermeshing gear type, as is also the motor-pump device 1. The specific details of construction of the pump and motor-pump device shown are so wellknown per se that they are not more extensively illustrated.

The valve mechanism 5 provides a chamber 16 to which hydraulic fluid is delivered by the conduit 4. From the chamber l6 fluid may be delivered through a shifter valve chamber I! to the connection l3 leading to the source I or, as

will shortly be explained, to another chamber l8 which is connected with the conduit 6 leading to the motor-pump device I and which communicates also with the shifter valve chamber I1 as will later be described. Desirably, the chambers I6 and I8 may be arranged in line with each other, as shown in Figs. 5 and 7, and separated by a ported septum 20 which provides a valve seat 2| which a check valve 22 is adapted to engage and against which said check valve is adapted normally to be maintained by a spring 23 which at one end engages the check valve and at its other end rests upon a plug 24 with which the conduit 6 is threadedly or otherwise suitably connected. The chamber I6 communicates with the chamber l8. of course, when the check valve 22 is unseated. Fig. 9 will aid in the comprehension of the structure of the, check valve 22, and from this figure it will be noted that the valve has a number of slots 25- in its periphery through which fluid may flow from the chamber Hi to the chamber l8 when the valve 22 is unseated.

acsaaee The shifter valve receiving chamber I I includes five annular chambers, each spaced from the next adjacent chamber by a ported partition. Starting from the top in Fig. 5, these annular chambers are successively numbered 26, 21, 28, 29 and 30. A ported partition 3i separates the chambers 26 and 21. A ported partition 32 separates the chambers 21 and 28. In like manner, ported partitions 33 and 34 respectively separate the chambers 28 and 29 and the chambers 29 and 30. Each of the ported partitions has the port therethrough of the same size as each of the others, said several ports being coaxially arranged so that their surrounding walls provide guidance for a two-spooled shifter valve 36 comprising an upper hollow spool 31, a lower spool 36 and a connecting portion 39 of reduced diameter, by reason of which an annular fluid con ducting groove 46 is provided between the spools 31 and 38, and a ported stop projection M. The spool 31 has a chamber or recess 42 in it, and a spring 43 extends into the recess and engages the lower end of the latter, the upper end of said spring 43 contacting an abutment plug 44 suitably packed at 45 to prevent leakage. A port 46, of relatively small diameter at its lower end 41 where it extends through the stop projection 4I, connects the chamber 42 in certain positions of the shifter. valve with the space surrounding the stop projection 4|. In other words, it connects the chambers'26 and 30, when open. The stop projection 4| of the valve is adapted to cooperate with a suitable abutment plug 48 and with a yieldingly mounted valve 49, of which more will be said shortly. The abutment plug limits the downward movement'of the shifter valve 36 and the valve 49 maintains closed the passage 46, 41 during its engagement with the projection 4|.

The annular chamber 26 communicates with the chamber I6 through a port or cored opening 50. Similarly, the annular space 2'|,communicates through a port or cored opening 5I with the chamber I6. Annular chamber 28 communicates through the conduit I3 with the conduit I I leading to the fluid source or reservoir I. The annular chamber 29 communicates through a port or opening 52 with the chamber 53 in a relief valve casing 54 shown in the drawings as a separate element from the main body of the valve mechanism as a whole, but obviously formable with it as a unit if desired. The annular space 30 communicates through an opening 55 with the chamber I8. The annular chamber 28 also communicates through a port opening 56 with a chamber 51 in another relief valve housing 58. The annular chamber 28 further communicates through an opening 59 with a chamber 66 in the relief valve casing 54. The annular chamber 26 communicates through an opening 6| with a chamber 62 in the relief valve housing 58. The chamber 53 is separated from the chamber 60 by a ported valve seat 64 with which a spring pressed relief valve 65 is adapted to cooperate. A spring 66 having a follower 61 is adjustably loaded by an adjusting screw and nut mechanism 68, which controls the compression of the spring 66 and thus determines the pressure at which the valve 65 will lift from the seat 64. A valve seat 69 surrounding a port I0 extending between the chambers 51 and 62 is adapted to be engaged by a relief valve II pressed in a closing direction by a spring 12 which engages a follower 13 whose position may be adjusted by a suitable screw and nut mechanism 74. The valves .65 and II have flowslots in the manner of valve 22. It will be observed that when the valve 36 is in top position, it does not prevent communication between the chamber l6 and the port ID. The normal compression of the spring I2 will be much higher than the normal compression of the spring 66, when their controlling valves have equal areas subjected to pressures tending to unseat such valves. For example, it may require a liquid pressure of 300 p. s. i. in chamber 62 to unseat valve I I, while for example a pressure of p. s. i. in chamber 53 will suffice to unseat valve 65.

The valve 49 consists of a head portion I5 and a plunger portion 16, the head portion being slidably received in a chamber 'I'I formed in the abutment plug 48, and the plunger portion 16 extending through a reduced opening I8 coaxial with the chamber 11. A spring 19 engages the head portion at one end, and at its other end engages an adjustable threaded follower 80, and the pressure exerted by the spring 19 may be determined by the adjustment of its follower 80. Normally the spring 19 tends to maintain the plunger I6 in the position shown in Fig. 7, but the valve 49 may be depressed to the position shown in Figs. 5 and 6 and the plunger portion I6 is adapted to 'seal the opening 41 in the several positions of the shifter valve illustrated in Figs. 5, 6 and 8, but does not seal the opening 41 in the position of the shifter ,valve shown in Fig. 7. It may further be noted that sealing of the opening 41 by the plunger portion 16 will be discontinued as the shifter valve 36 moves upward, only, with the proportions shown, when the shifter valve reaches a position at which the flow of fluid through the port 5| and through the annular recess or groove 23 and the connection I3 has commenced. This means that the shifter valve will be sharply thrown, as the pressure at its upper end will drop when chamber I6 is connected with vent line I3. The mode of operation of the valve element 49 and its cooperation with the other parts of the mechanism will be more fully explained shortly.

The pump 3 may be considered, for the purposes of explaining the mode of operation of the invention, to be driven continuously while the vehicle is in use. Accordingly, it is taking liquid from the reservoir. or source I, through the conduit 2, and discharging it through the conduit 4 into the chamber I6, and the fluid that enters the chamber I6 must obviously go somewhere. Some of it can go through the conduit 6 after passing the check valve 22, and cause the motorpump device I to operate as a motor and effect a winding in of the cable I0, and then pass back to the source I through the conduit II, if the cable can be reeled in. However, the rate at which the cable can be wound in may and probably will be entirely insuiiicient to permit all of the fluid delivered by the pump 3 to pass through the motor-pump device I and, indeed, it is possible that the motor-pump device may be entirely incapable of winding in the cable at all, as when the vehicle is at a standstill. Therefore, some of the liquid delivered to the chamber I6 must go elsewhere, and this it will do, passing by way of the passage 50, the annular groove 26, the passage BI, the chamber 62, the port 10, past the check valve II, through the chamber 51, the passage 56, the groove 28, and the conduit I3 into the return line I I and back to the source or reservoir I. The pressure of the spring 12 will be made sufficient to compel the desired pressure to be maintained in the chamber I6, and in the conduit 6. For example, a, pressure of 300 p. s. i. may be maintained in the fluid supply connections to the motor-pump device 1 by the appropriate setting of the spring '12. In Figs. and 11', it may be noted that in order to avoid overlapping ports the connection of the conduit I3 with the chamber 28 is' shown as made by way of a portion of the conduit 56 instead of opening into the chamber 28 separately from the port 56 and at right angles to the communication of that port with the chamber 28. Fig. 11, subject to the understanding just expressed, may be considered to show the normal position of the parts during the operation of the motor-pump device 'i as a motor to effect winding in of the cable 10, in other words, the mode of operation which takes place when the vehicle is moving in a direction to shorten the free length of the cable. At this time the shifter valve 36 occupies the position shown in Figs. 5 and 6 as well as Fig. 11 and is held in that position by reason of the facts .(a) that the hydraulic pressure on its lower end is less than the hydraulic pressure on its upper end by the amount occasioned by the presence of the spring 23, and (b) that the spring 43 operates to hold the shifter valve 36 in the position mentioned.

If the vehicle is brought to a stop, the motorpump device 7 will no longer drive the reel to wind in the cable, because the cable cannot then ordinarily be wound in; but there will be nothing which will occur in the controlling apparatus which would cause movement of the shifter valve 3'6 to reduce the pressure imposed on the motorpump device I and so the cable will remain under undiminished tension while the vehicle is at a standstill. It will be noted that in the position of the shifter valve 36 shown in Figs. 5, 6 and 11, the lower end of the projecting portion 4| engages the top surface of the plug 48 and and the plunger portion 16 of the valve 49 contacts the end of the projecting portion 4! and acts as a valve associated with the passage 41, and, because the spring 19 is strong enough to maintain this contact against the pressure for which the relief valve 1! is set, no flow through the passage 41 downwardly or upwardly will be possible until the shifter valve is moved up such a distance that contact between the plunger portion 16 of the valve 49 and the lower end of the projecting portion 4| of the shifter valve is interrupted.

Now suppose that the vehicle is caused to move in the direction which will necessitate the unwinding of the cable from the reel in order for such motion to take place. The tension of the cable will require the motor-pump device I to rotate in such a direction as to pump fluid taken in through the conduit ll into the conduit 6. This fluid will pass into the chamber I8, but cannot pass the valve 22, and it also will be unable to pass the shifter valve'36 in the lower position of that valve. Accordingly there will be an instantaneous building up of pressure below the shifter valve 36 to a value in excess of the pressure existing on the top of that valve supplemented by the strength of the spring 43, and the shifter valve will start to move upward. The valve 49 will be moved upward by the spring 19 as long as there is no contact between the head portion of the valve 49 and the portion of the plug 48 above the bore 11. Thus there can be no flow of fluid from the space below the shifter valve to the space above it, and the greater pressure below this valve will be maintained until the shifter valve gets well under way and preferably moves upward to such a point that the groove 40 can connect the port 51 with the annular chamber 28 and with the conduit l3 and thus permit a relief of the pressure at the upper end of the shifter valve. After this relief in pressure takes place, it will require no great pressure below the shifter valve to complete its travel and to maintain it in raised position, and whenthe shifter valve reaches top position the fluid pumped by the motor-pump 1 will be permitted to pass through the opening 52 and past the lower set relief valve 65 into the port 59 and through annular chamber 28 into the conduit l3, but it will be noted that the pressure acting to maintain the shifter valve in raised position will still exceed the pressure tending tov force it down again by reason of the fact that the force produced by the spring 43 and the freely venting discharge of the pump 3 will not be equal to the pressure resulting from the presence of the relief valve 65 with its loading spring 66.

To repeat, the back pressure on the main pump is completely removed except for such resistance as friction of the liquid in the passages may involve, when the shifter valve is maintained in top position, and this shifter valve will be maintained in top position because of the greater pressure imposed on its lower end by reason of the presence of the relief valve 65. and its loading spring 66, this relief valve being adapted to maintain a pressure of, for example, p. s. i. in the chamber 53. By reason of the structure described, the tension on the cable I0 will be substantially reduced, and the reel may be turned backward, driving the motor-pump device 1 as a pump, with a much lower pressure in the line 6 than during the operation of the motor-pump device as a motor.

Now let it again be assumed that the vehicle stops. The motor-pump device 1 no longer acts as a pump and no longer delivers fluid through the conduit 6. Since the valve 49 is not sealing the passage 41, in the raised position of the shifter valve; the latter will move downwardly freely upon the cessation of the pumping of fluid into the chamber [8, until the lower end of the projecting portion 4| contacts the plunger portion 16 of the valve 49, and at the time the communication between the port 5| and the line I3 has, with a desirable proportioning of the parts, been interrupted, with the result that the pressure above the shifter'valve will build up to the full amount called for by the setting of the relief valve H. Thus, even though the shifter valve did not go all the way down to its position shown in Figs. 5 and 6, the pressure would build up to the setting of the relief valve H and the cable would be placed under tension, ready for immediate winding in if the vehicle starts to move in a direction in which winding up of the cable will be requisite. If the passage 46, 41 were sealed off slightly before the communication between the passages 5i and 28 was completely interrupted, still, the throttling of the pump discharge could be counted on to cause a sufficient increase in the pressure above the valve 36 to cause the latter to move down to its bottom position.

It will be observed that the valve 49 prevents flow of fluid longitudinally through the valve 36- from the lower to the higher end thereof-until the valve has reached a position in which the groove 40 between its spools comes into communication with the passage 51, and it may further be noted that the strength of the spring 19 aosaaaa contact with the lower end of the shifter valveand seal the passage through the latter so long as the shifter valve is within the range of movement of the valve 49. In passing it may be noted that fluid locking of the valve 49 is prevented by the provision of adequate clearance around its head 18 and plunger portion 18.

One important feature of the arrangement so far described is the provision of means -which seals a passage through the shifter valve as long as the latter is below positions in which the passages ii and 28 are not in communication with each other, and, more broadly, there is presented by the invention a shifter valve having chambers above and below it and withmeans provided for the interconnection, through a restricted passage, of such chambers in predetermined positions of the shifter valve, with said passage automatically sealed when the shifter valve is below positions in which communication between the grooves 21 and 28 exists. .80 viewed, it will be appreciated that in its broader aspects my invention is also present in the modifications of Figs. l2.and 13, and also in the modifications of Figs. 14 and 15, now to be described.

.Referring first to the former figures (Figs. 12 and 13) it will be noted that the valve 49' has a head 85 which has a close sliding fitwith the bore 48' extending through the shifter valve 38', except at the lower enlarged end 88 of such bore, where there is such an increase in diameter that when the head 85 lies wholly in the enlarged end 86, fluid can pass freely through the passage or bore 48' and the enlarged lower end thereof. The valve 49' may be made of uniform diameter, instead of having a head larger than its supporting stem 85'. The longitudinal extent of the en-- larged bore 86 and the position of the upper end of the head 85 will be so determined that communication will be established between the chambers 28 and 30, desirably, just as connection is established between the grooves 21 and 28. The valve 49' is secured, in this embodiment, to a screw plug 81, threadedly secured in the bottom plug 48'. As may be seen from Fig. 12, there is no substantial passage of fluid from the chamber 30 to the chamber 28 when the shifter valve is in its lowermost position of Fig. 12, or before the passage and the groove 28 are interconnected, but in the upper position of the shifter valve, the chambers 30 and 26 freely communicate with each other through the bore 46'.

In both of the forms of the invention so far described in some detail, ready adjustment of the positions of the valves, respectively, 49 and 49 is possible, and the passages which are adapted to connect the chambers 26 and 30 traverse the shifter valves. It is possible, however, as shown in Figs. 14 and 15, to make the shifter valve 36" imperforate from end to end, and to provide a passage 90 in the body of the valve device 5, and to connect this passage by transverse portions 9| and 92 respectively with the chamber 28 and with the shifter valve receiving bore just above the chamber 30; and, by the proper location of the point of opening of the transverse portion 92 through the cylindrical wall portion 93 of the bore which receives the shifter valve 38", to seal communication between the chambers 28 and 30 when the shifter valve is in positions in which the passage 5| and the chamber 28 are not in communication with each other, and to provide communication through the passages 9|,

80, 82 between said chambers 28 and 88 at other ,times.

From the foregoing description, it will be evident that my invention may be embodied in various forms, and that in all of the forms .the operation will be positive and definite, and independent of the viscosity of the hydraulic fluid used, and that even if the oil gets very hot and there might otherwise be a tendency for it to flow so freely through the passage connecting the chamber 80 with the chamber 28 as to render the action of the shifter valve less positive than would be desirable, nevertheless, in each embodiment disclosed, the means for preventing flow between such chambers until the valve has gotten well started on its upward movement and connects the passage 5| with the chamber 28, will make certain and snappy the shifter valve control.

While there are in this application specifically described a preferred form, and two modifications, of my improved control valve, it will be understood that this form and these modifications are shown for purposes of illustration and that the invention may be further modified and embodied in various otherforms without departing from its spiritor the scope of the appended claims.

What -I claim as new and desire to secure by Letters Patent is:

1. In combination, in a valve mechanism, a casing having in it four valve-containing chambers, a shifter valve in one of said chambers, a relief valve, having one setting, in another of said chambers, another relief valve, having another setting, in still another of said chambers, and a check valve in the fourth one of said chambers, each of said relief valves and said check valve controlling flow through its respective chamber, an external connection having communication with one end of said shifter valve chamber and also communication with that chamber at a point spaced from both of its ends and also, when saidcheck valve is unseated,. with the chamber containing said check'valve and, when the relief valve therein is unseated, with one of said relief valve containing chambers; an internal connection communicating with said shifter valve chamber, at another point in the latter between its ends, and, when the relief valve therein is unseated, with the chamber containing the other relief valve, another external connection communicating with the otherend of said shifter valve chamber and with said check valve containing chamber, and a third external connection having communication with the chambers containing each of said relief valves and with said shifter valve chamber at a still different point between the ends of the latter, said shifter valve being responsive to the fluid pressures in the opposite ends of said shifter valve chamber and having portions respectively connecting said first and third external connections together and connecting said internal and said second mentioned external connection together in one extreme position of said shifter valve and portions interrupting such connections in the other extreme position of said shifter valve, and means for connecting together the opposite ends of said shifter valve chamber only when the shifter valve is at least a predetermined distance from said other end of its chamber.

2. The combination defined in claim 1 in which 11 said means for connecting together the opposite ends of said shifter valve chamberis governed by the position of said shifter valve.

3. The combination defined in claim 1 in which said means for connecting together the opposite ends of said shifter valve chamber includes passage means extending in a direction lengthwise of said shifter valve and communicating continuously with the first mentioned end of said shifter valve chamber, and connected with said other end of said shifter valve chamber when said shifter valve is at least such predetermined distance from that end of said chamber.

4. The combination defined in claim 3 in which said means for connecting the opposite ends of said shifter valve chamber includes passage means extending axially of said shifter valve and communicating continuously with the first mentioned end of said shifter valve containing chamber, and valve means is supported at said other end of said shifter valve containing chamber for preventing flow through said passage means in said chamber valve except when the latter is at least such predetermined distance from that end of said chamber.

5. The combination defined in claim 4 in which the valve means supported at said other end of said shifter valve chamber is yieldably sup-- ported at such end and is engageable with one end of said shifter valve.

6. The combination defined in claim 1 in which said means for connecting the opposite ends of said shifter valve chamber includes passage means extending axially of said shifter valve and communicating continuously with the first mentioned end of said shifter valve chamber, and valve means is yieldably supported at said other end of said shifter valve chamber and projects yieldingly into said chamber and is engageable with one end of said shifter valve for preventing flow through said passage means in said shifter valve except when the latter is at least such predetermined distance from said other end of said chamber.

'7. In combination, in a valve mechanism, casing means providing chambers including a shifter valve chamber and two relief valve chambers, a supply chamber, and, in communication with said supply chamber, a check valve chamber, a shifter valve in said shifter valve chamber, passage forming means connecting the opposite ends of'said shifter valve chamber and opened and sealed in different positions of said shifter valve, relief valves, having different loadings, in said relief valve chambers, a check valve in said check valve chamber, a connection at the exterior of said casing means communicating with said supply chamber, a second connection at the exterior of said casing means, said second connection communicating with said check valve chamher, a third connection at the exterior of said casing means, said third connection communicating with said shifter valve chamber at a point between the ends of the latter, means establishing communication between said supply chamber and one end of said shifter valve chamber, means establishing communication between said check valve chamber and the other end of said shifter valve chamber, means establishing communication between each of said relief valve chambers and the exterior of said casing means via said third connection at the exterior of said casing means, means establishing communication between said supply chamber and the seat end of one of said relief valves, means $iablishing 12 communication between the supply chamber and the seat end of said check valve, means establishing communication between said shifter valve chamber and the seat end of the other one of said relief valves, and means establishing communication between said supply chamber and said shifter valve chamber at another point therein, said shifter valve having portions for effecting, in one position thereof, a connection between said last mentioned communication establishing means and the point in said shifter valve chamber which is in communication with the third connection at the exterior of said casing means and for effecting, in the same position thereof, a connection between said other end of the shifter valve chamber and said means for establishing communication between said shifter valve chamber and the seat end of the other of said relief valve means, and said shifter valve having portions for interrupting the connections it establishes in said one position thereof, when it is moved to another position.

8. The combination defined in claim '7 in which the passage forming means connecting the opposite ends of said shifter valve chamber, and opened and sealed in different positions of said shifter valve is a passage extending longitudinally through said shifter valve.

9. The combination defined in claim 7 in which the chambers provided by said casing means have parallel axes and the passage forming means connecting the opposite ends of said shifter valve chamber, and opened and sealed in diiferent positions of said shifter valve is a passage extending longitudinally through said shifter valve.

10. In combination, in a valve mechanism, casing means providing chambers including a shifter valve chamber and two relief valve chambers, a supply chamber, and, in communication with said supply chamber, a check valve chamber, a shifter valve in said shifter valve chamber, relief valves, having different loadings, in said relief valve chambers, a check valve in said check valve chamber, a. first connection at the exterior of said casing means in'communication with said supply chamber, a second connection at the exterior of said casing means, said second connection in communication with said check valve chamber, a third connection at the-exterior of said casing means, said third connection communicating with said shifter valve chamber at a point between the ends of the latter, means establishing communication between said supply chamber and one end of said shifter valve chamber, means establishing communication between said check valve chamber and the other end of said shifter valve chamber, means establishing communication between each of said relief valve chambers and the exterior of said casing means through said third connection at the exterior of said casing means, means establishing communication between said supply chamber and the seat end of one of said relief valves, means for establishing communication between the supply chamber and the seat end of said check valve, means establishing communication between said shifter valve chamber and the seat end of the other of said relief valves, means establishing communication between said supply chamber and said shifter valve chamber at another point therein, means for biasing said shifter valve towards one end of its chamber, means for providing a restricted communication between the opposite ends of said shifter valve chamber, and means at the end o S id Shifter valve chamber towards 13 which said shifter valve is biased for controlling the communication between the opposite ends of said shifter valve chamber, said shifter valve' having portions for effecting, in one position thereof, a connection between said last mentioned communication establishing means and the point in said shifter valve chamber which is in communication with the third connection at the exterior of said casing means and for effecting, in the same position thereof, a connection between said other end of the shifter valve chamber and said means for establishing communication between said shifter valve chamber and the seat end of the other of said relief valve means, and said shifter valve having portions for interrupting the connections it establishes in said one po-' sition thereof, when it is moved to another position.

11. In combination, in a valve mechanism, a casing having a fluid supply connection and having in communication with said fluid supply connection a chamber for a shifter valve, a relief valve set for the venting of fluid at a relatively high pressure and a check valve, said casing further having therein another relief valve set for the venting of fluid at a relatively lower pressure, and said casing having a connection adapted to serve as a delivery passage for fluid passing said check valve or for a return of fluid to said casing, said second connection communicating with said shifter valve chamber at one end of the latter and said first, fluid supply connection having its communication with said shifter valve chamber at the other end of the latter, said shifter valve chamber having a vent connection and said shifter valve chamber having therein a shifter valve responsive to the pressures in the opposite ends of its chamber and operative in one extreme position thereof to connect said fluid supply connection with said vent connection and to connect said second connection with said lower set relief valve, means associated with said shifter valve for establishing communication between the opposite ends of its chamber in predetermined positions of said valve, and means for preventing such communication except when said shifter valve is in a position to effect a connection between said fluid supply connection and said vent connection.

12. A valve mechanism as recited in claim 11, in which said means associated with said shifter valve for establishing communication between the opposite ends of its chamber is constituted by a passage extending longitudinally through said shifter valve, and said communication preventing means is a valve carried by said casing and adapted to seal said passage in certain predetermined positions of said shifter valve.

13. A valve mechanism as recited in claim 11, in which said means associated with said shifter valve for establishing communication between the opposite ends of its chamber is constituted by a passage extending longitudinally through said shafter valve, and said communication preventing means is a valve yieldably supported by said casing in a position in line'with said passage and having a limited motion relative to the latter less than the motion of said shifter valve.

RICHARD J. HOPKINS.

References Cited in the file of this patent UNITED STATES PATENTS Nurfiber Name Date 1,955,154 Temple Apr. 17, 1934 2,395,302 Slomer Feb. 19, 1946 2,467,238 Slomer Apr. 12 ,1949 2,472,694 Chouings June '7, 1949 

